Inaccuracy of Breed Labels

Inaccuracy of Breed Label
s Assigned to Dogs of Unknown Origin

Victoria Voith, PhD, DVM, DACVB, and colleagues from Western University of Health Sciences originally compared the breed identifications assigned by adoption agencies to dogs of unknown parentage with DNA breed analysis of the same dogs. They found low agreement between the two. Their findings, first published in 2009, are presented in the following two documents:

Two separate, additional studies conducted at the College of Veterinary Medicine at the University of Florida, further confirm the unreliability of visual breed identification used by dog adoption agencies, animal control (lost and found), and in regulation. Click below to read NCRC's two whitepapers discussing the significance of the findings in each, and to view the poster associated with the first study.

Observers Don’t Agree on Breed Identifications

In a second paper published in 2013, Dr. Voith and her colleagues surveyed more than 900 people in dog-related professions and services and showed that respondents frequently disagreed with each other when making visual breed identifications of the same dog, and that their opinions may or may not have correlated with DNA breed analysis.More than 70% of the study participants reported that now or at one time, their breed descriptors were used in record keeping. The results of the survey call into question the validity of a variety of data that has been collected over the decades pertaining to breed identification of dogs.
Reliabiltiy of DNA Breed Identification
We take very seriously the reliability of the studies on which we report and understand that there are those who are skeptical of breed identification obtained through DNA analysis. And indeed, it is important to note that DNA identification is not 100% accurate when analyzing mixed-breed dogs, nor do the companies who conduct the analyses claim it to be so. At the time Dr. Victoria Voith conducted the first of these studies, the accuracy of the Mars Wisdom Panel® used in the studies was reported to be 84%, for identification of breed in F1 crosses (offspring of 2 different registered purebreds). Accuracy is currently reported to be 90%. The Mars Wisdom Panel®, is specifically intended for mixed-breed dogs. The test was developed by analyzing more than 19 million genetic markers taken from 13,000 dogs.

We can say with confidence, that this documented rate of accuracy for DNA analysis is much higher than that achieved by looking at the dog for at least 2 reasons:
•In Genetics and the Social Behavior of the Dog, a seminal work on dogs and the significance of documented pedigree, John Paul Scott and John L. Fuller showed that that even F1 crosses very rarely have much physical resemblance to either of their parents’ breeds.
Understanding how a dog's appearance is determined by its DNA helps explain why the DNA test is better than a visual breed identification. Visual identification is based upon the observation of a handful of variable breed-associated physical traits, such as coat color, body size, skull shape and whether the ears or erect or floppy. These physical traits are found in many different breeds and are controlled by approximately 50 of the roughly 20,000 genes that create a dog. Sometimes, a breed may exhibit a certain physical trait because all the members in the breed have exactly the same version of the gene that encodes the trait.
If this trait is recessive (for example like the trait associated with long fur), only dogs with two of the same version of the gene will exhibit long fur. If one of these dogs is the ancestor of a mixed- breed dog, the mixed-breed dog may contain both the DNA for the recessive version of the trait (long fur) and the dominant version of the trait (short fur). However, the long-haired recessive appearance will not be observed because the dominant short-haired DNA would determine the visual appearance of coat length (making it short). Subsequently, the visual identification of breed would inaccurately specify short-haired breeds based upon the visual observation of short hair.
The DNA test would be able to detect the recessive version of the gene for the long hair along with the dominant version of DNA for the short-hair and the DNA test result would use that information to determine the breed. The DNA results might report both long-haired and short-haired breeds in the dog's ancestry even though the dog only has short-hair. Coat length is not the only trait that can be "hidden" from visual observation due to dominant and recessive patterns of genetic inheritance in dogs.

Although the genetic test may not assess every gene or even each physical attribute of a dog, the regions of the genome that it uses to assess breed take into account much more information than visual observation. The DNA test is better than visual breed identification because it takes into account the pattern of genetic variation at many different regions across the dog genome to generate a "genetic snapshot" of a mixed-breed dog's ancestry. The resulting genetic evidence for what breeds make up a mixed-breed dog may or may not agree with visual observations, but they do agree with what scientists have discovered from two decades of sequencing and studying genomes.

While breed identification by DNA analysis is more accurate than visual breed identification, it’s important to remember that neither identifies genetic markers influencing specific traits, or predicts behavior of any particular dog. Each dog is an individual, and its physical and behavioral traits will be the result of multiple factors.